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Researches and Applications for Automotive Field
Andrea Azzali, Eraldo Carpanoni, Angelo Farina
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Topics

• Main Researches
• Objective evaluation index for audio performance
  characterization and Innovative Analysis
  technique for musical signal (AQT system)
• Virtual car cockpit for system comparison
• Algorithm for audio equalization (AQT, CTC)
• Simulation of digital system staying inside car
  cockpit
• Robust measuring technique for reliable and
  stable characterization with IR

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• Innovative dynamic analysis technique

AQT Tool
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Innovative dynamic analysis technique

• Goal
• Substitute classical analysis based on FFT with
  dynamic analysis
• Reasons
• FFT characterize system only in steady state
  condition
• BUT
• Hearing system is more sensible vs transient
• Musical signal is not a steady state signal
• Solution
• Aqt analysis system

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AQT Analysis system

• Features
• Use transient stimulus instead steady-state ones
• Find psychoacoustics response more closed to real
  perceived curve than FFT response
• Find resonance in cockpit and tail that affect
  hearing
• Useful during car system development
• Output
• Articulation parameter
• Energy deviation from best curve corresponding to
  pleasant hearing inside the car

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Objective evaluation system
Evaluation Test
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Objective evaluation system

• Activity in Collaboration with CRF Fiat Research
  Centre
• Goal
• Reduce time needed for system characterization
  during car system development
• Obtain Reliable characterization of hearing
  inside the car and develop a series of objective
  parameter useful as project statement
• Status
• In progress (deadline 24/12/2003)

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Objective evaluation system

• Proceeding
• Study of main features that affect subjective
  evaluation of car system gtgt OUTPUT Subjective
  Index of performance (New IPA)
• Study of a series of objective parameter able to
  describe this features gtgt OUTPUT statement
• Study of correlation between subjective and
  objective parameter gtgt OUTPUT Objective Index of
  Performance

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Objective evaluation system

• Subjective evaluation parameters
• Intensity of Sound and SPL MAX.
• Distortion.
• Spectral attributes.
• Spatial attributes .
• Speech clarity and intelligibility.
• Low frequency quality.
• Articulation and clarity of sound (Fidelity)
• Objective Parameters
• Dynamic response of car inside (AQT Method)
• Articulation and energy recovery at low frequency
  (AQT)
• Spatial parameter (IACC and localization index)
• Speech clarity (STI)
• ..

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Objective evaluation system

• Current activities
• Preparation of subjective test based on
  questionnaire developed for subjective database
  and statistical process
• Study of listening room as standard listening
  test environment instead of car inside

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Virtual listening system
Listening room
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Virtual listening system

• Goal
• Fast comparison between different car audio
  system
• Detailed highline of difference
• Reasons
• The tests not be done in the car because of the
  high switching time and the unavailability of the
  car after long time.
• Features
• Fast switch between different configurations
• Capability of comparison by audio system of the
  cars nevermore available
• The listening room reproduce the binaural
  recorded tracks in the car and doesnt insert any
  apparent alteration.

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Virtual listening system

• Proceeding
• Record with dummy head Audio CD for subjective
  test and signal for characterization of car
  inside
• Reproduce the Audio track, recorded in several
  car, in Virtual system
• Use for audio comparison an automatic software
  developed in VB

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Virtual listening system

• Virtual system
• Double stereo dipole
• Two central channel for voice and monophonic
  signal
• Two surround channel for reproduction of high
  uncorrelated signal and aimed to recreate lateral
  contribution from loudspeaker in car

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Virtual listening system
Virtual system Plant
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Algorithm for sound field correction
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Algorithm for sound field correction

• Existing algorithms
• Time delay alignment
• Stereo dipole for new configuration system
  (dedicate loudspeaker central channel)
• Psychoacoustic curve correction (Aqt Filter)
• Algorithms under test
• Stereo dipole for standard system configuration
• Resonance and tail correction system (Aqt Filter)
• In the future gtgt Surround system 51
• Platform
• DSP board
• Technique
• FIR Filtering

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Algorithm for sound field correction

• Time delay alignment
• Compensate the time difference existing between
  the time arrival of the direct sound of the two
  hearing channel
• Create a virtual symmetric system
• Enhance spatial sensation and create a wide scene
  in the driver position
• Stereo dipole for new configuration system
• Need a couple of loudspeaker for each seat
• Enhance spatial sensation and create a wide scene
  in all the listening position
• Perform Cross-Talk and reduce resonance and
  reflection effects on the hearing

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Algorithm for sound field correction

• Psychoacoustic curve correction
• Invert dynamic curve response of car cockpit
  really perceived by hearing system
• Perform more pleasant filter than standard
  inversion technique
• A tool is already developed to perform this AQT
  Tool

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Digital system simulation
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Digital system simulation

• Overview
• its a difficult task compare a lot of algorithm
  and set of coefficients at the same time on DSP
  board
• Solution gtgt Simulation System on PC
• Goal
• Simulate different digital system for correction
  of the response inside the car Stereo Dipole
  Filtering, IIR, FIR,AQT Filter, 51 surround
  system
• Compare different configuration staying in
  listening position
• Features
• Let us to compare all the algorithms in real time
  and perform a fast switching between different
  configuration (Ex 51 vs Cross Talk)
• Let us to compare in a fast way several set of
  coefficients of FIR, IIR, AQT filter and to
  choose the set that retrieves the best
  performance and pleasure
• PERMIT ON THE ROAD TEST!!!

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Car inside digital system simulation

• Simulation system
• A Notebook
• Existing Software
• digital block performing several algorithm
• Accept extern block programmed in VST standard
• We already have all the block that permit the
  simulation of the entire set of developed
  algorithm
• We have the know-how to perform new VST plug-in
  for new algorithm
• A multichannel (10 or more) Sound Card with
  PCIMCA interface as Echo Layla gtgt WE NEED IT!!!
• Amplifiers to drive all the loudspeaker

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Car inside digital system simulation

• Simulation Block Diagram

Standard system
PCIMCA Multichannel Audio card
Multichannel Power Amplifier
Notebook
Stereo dipole system
51 surround system
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Reliable measure technique
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Reliable measure technique for IR

• Goal
• Introduce the Impulse Response as standard
  measure for characterization of the car inside
• Introduce the use of Cool-Edit and Aurora for IR
  measure
• Introduce AQT Tool as advanced analysis system
• Perform reliable and repeatable measures of
  response inside the car testing several
  procedures of average of binaural recording
• THE ACTUAL APPROACH Binaural recording of IR
  with rotating dummy head by step of 15 degrees